The primary focus of the proposed research is to delineate the molecular mechanisms through which intracellular tension regulates endothelial cell proliferation. Vascular cell types, including endothelial and smooth muscle cells respond to a variety of cell growth control signals including soluble growth factors, adhesion to the extracellular matrix (ECM), and physical forces resulting from cell spreading (changes in projected cell area) and fluid shear stress. Diseases such as atherosclerosis are characterized by excessive proliferation of vascular cell types, thus a major hurdle to treating vascular disease is a complete understanding of the growth control mechanisms governing the proliferation of vascular cells. Based on preliminary data generated in our laboratory, we hypothesize that intracellular tension generated through the RhoA signaling pathway is a key regulator of endothelial cell proliferation. In this proposal we plan to investigate the signaling pathways which link endothelial cell spreading and establishment of intracellular tension to proliferation. The proposed research will use a molecular genetic approach coupled with microfabrication technologies to investigate tensional pathways leading to cell proliferation. Specifically, we plan to use microcontact printing techniques to limit cell spreading while expressing signaling proteins involved in intracellular tension generation, including RhoA, and ROCK. Furthermore, a novel cellular tension microsensor will be used to directly measure intracellular tension in response to manipulation of these pathways. This project will provide insight into the molecular mechanisms controlling endothelial cell proliferation and ultimately, this understanding may lead to better treatment strategies for vascular disease.